微乳法合成纳米SiO2/TiO2及其光催化性能

采用聚乙二醇辛基苯基醚(Triton X-100)/正己醇/环己烷/氨水微乳体系合成了纳米TiO2和SiO2/TiO2复合物,用X射线衍射、红外光谱和透射电镜对其结构进行了表征,并以甲基橙降解评价了其光催化性能,讨论了SiO2/TiO2摩尔比、晶相组成及粒径与光催化活性的关系.结果表明,SiO2/TiO2催化剂中形成了新的Ti-O-Si键和无定形SiO2;在纳米TiO2中复合SiO2能有效抑制锐钛矿向金红石的转变,增加锐钛矿的稳定性,并阻止TiO2晶粒的聚集生长.催化剂的光催化活性随金红石含量的增加而降低,加入适量SiO2能明显提高TiO2的光催化活性,其中摩尔比为1/7的SiO2/TiO2光催化活性最高.

Microemulsion Synthesis of Nanosized SiO2/TiO2 Particles and Their Photocatalytic Activity

Nanosized TiO2 and SiO2/TiO2 particles were synthesized by hydrolysis of tetrabutyl titanate and tetraethyl orthosilicate in a Triton X-100/n-hexanol/cyclohexane/ammonia reverse microemulsion. The particles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy. The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange under UV light irradiation. The effects of SiO2 content, crystal structure, and crystallite size on the photocatalytic activity were investigated. From FT-IR analysis, a new band at 950 cm-1 for Ti-O-Si vibration was observed. Ti-O-Si bond and amorphous SiO2 suppressed the phase transformation of titania from anatase to rutile, increased the stability of anatase TiO2, and inhibited the growth of crystallite. The average size of titania decreased from 38.4 nm in pure TiO2 to 3.9 nm in SiO2/TiO2 with a SiO2/TiO2 molar ratio of 2/1. In addition, the photocatalytic activity decreased with the increase of rutile content. SiO2/TiO2 particles with a SiO2/TiO2 molar ratio of 1/7 showed the highest photocatalytic activity for the photocatalytic degradation of methyl orange.